Single reel data tape cartridges, one generation of which is known as 3480 type cartridges, include a reel containing magnetic tape with a leader block attached to the free end of the tape as it extends from the reel. The cartridge is generally rectangular except for one corner which is angled and includes a leader block window. The leader block window holds the leader block and permits the tape to exit from the cartridge for threading through a tape drive when the leader block is removed. When the leader block is snapped into the window, the window is covered.
The leader block is generally rectangular and has a cutout which combines with a pin to hold the tape. The front surface of the leader block includes a slot for engaging an automatic threading apparatus in a reel-to-reel magnetic tape drive apparatus. The front surface of the leader block is generally cylindrical and has a rounded boss which engages with an inclined surface of the corner of the cartridge. The rear surface is rounded to form a portion of an arc of a radius to match the periphery of the take-up reel hub in the tape drive apparatus as the leader block fits into the slot in the hub. A compliant section may be formed on the leader block to permit the leader block to compress at its rear surface to accommodate especially the first layer of tape when the tape is wound onto the take-up reel.
The tape drive apparatus includes a threading apparatus for connection to a single reel tape cartridge. The drive apparatus includes a drive motor for the supply reel mounted beneath a base plate so that its shaft extends normal to and slightly above a surface of the base plate. A take-up reel is mounted on the base plate and is attached to the motor. The cartridge reel, when coupled to the motor, lies in substantially the same plane as a hub of the take-up reel so that the tape moves in a plane normal to both motor shafts when being transported. After the threading of the tape, transfer of the tape between the supply reel and the take-up reel is achieved by controlling the driving motors for the reels. The tape passes through a vacuum guide, a magnetic transducer head, and a tension transducer.
The tape cartridge is formed of a molded base and cover which are ultrasonically welded to each other to form the housing for the cartridge. A small weld bead is molded into the bottom surface of the walls of the cover. This weld bead mates with the top surface of the walls of the base. The sonic energy is generally applied through the cover and to the weld bead to melt the bead onto a land on the base and cover. It is also known to locate the weld bead on the base.
Proper assembly requires proper registration of the base and cover and proper collapse of the weld bead during welding. However, improper registration can yield poor control of the outer dimensions of the cartridge and increase external and internal flash due to reduced clearances. In extreme cases this can prevent the weld bead from contacting the mating wall surface of the base. This can result in poor weld strength and cartridge failure if the cartridge is stressed such as by being dropped. In less extreme cases, it can result in an increase in exposed flash and reduced strength. Nonuniform weld bead collapse also can result in poor weld strength and cartridge failure if the cartridge is stressed. Proper collapse depends on proper positioning and support of the base and cover during welding, and on proper balance of the input ultrasonic intensity. Also, welding of the housing assembly can result in weld flash escaping from the interface between the base and the cover if the joint width and flash area are insufficient to contain the flash created when welding to the designed weld depth. Raised walls are designed into the inner walls of the base or the cover to minimize weld flash escaping into the inside of the cartridge where it can affect the tape and cause errors. Flash on the outside of the housing is cosmetically objectionable.
The base of these known cartridges includes raised wall sections which serve as locators to help align and locate the cover with respect to the base during assembly. These locators operate in only one direction and are essentially ineffective as flash retainers.
There is a need to provide a cartridge base and cover assembly which reduces the amount of weld flash that is generated during welding while maintaining sufficient weld strength to resist the propagation of cracks when the cartridge is stressed. There is a need for a single reel cartridge assembly which prevents flash escaping from the interface between the base and the cover either into the cartridge or outside of the cartridge. There is also a need for a system to improve the assembly of the housing by facilitating alignment of the cover and the base.